'Cool' Fiber Light Source Inspected

Photonics.comMar 2007
ANAHEIM, Calif., March 30, 2007 -- A light source based on fiber-optic technology that could improve the inspection of food, produce, paper, currency, recyclables and other products was the topic of a presentation at OFC/NFOEC 2007.

Industrial processes for inspecting food products and other items now often use "line-scan" cameras, which record images of objects a line at a time, the way fax machines scan documents on a line-by-line basis. Rapid electronic processors then detect any problems and instruct mechanical actuators (such as air jets) to separate out unsatisfactory items.

Current line-scan cameras lack ideal light sources to image objects properly, said Princeton Lightwave of Cranbury, N.J. and OFS Labs -- a Somerset, N.J.-based division of Furukawa Electric. The companies described a fiber-optics-based solution, in which a bright light source, such as a laser, sends light through an optical fiber. Along the length of the fiber is an ultraviolet-light-treated region, or fiber grating, which deflects the light so it exits perpendicularly to the length of the fiber as a long, expanding rectangle of light. This optical rectangle is then collimated by a cylindrical lens so the rectangle illuminates objects of interest at various distances from the source. The bright rectangle allows line-scan cameras to sort products at higher speeds with improved accuracy, the companies said.

They said the new fiber-based light source combines features necessary for accurate and efficient scanning: uniform, intense illumination over a rectangular region; a directional beam that avoids wasting unused light by only illuminating the rectangle; and a "cool" light source that doesn't heat up the objects to be imaged. Typical light sources, such as tungsten halogen lamps or arrays of light-emitting diodes, lack at least one of these features, they said.

According to the researchers, this fiber-based device can be customized for a specific inspection application within four to six weeks, then manufactured for that application in 16 to 20 weeks.

The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...